Understanding Solar chargers:

So what in a good portable solar charger....

you got panels and electronics....

So if I got a 5w panel I am right for charging basic stuff?? Sure 5w charging power is heaps for charging batteries ect, so all I need is good panels right?? WRONG, this is where is gets confusing....due to the way solar panels actually work....

you can have a 5w panel and electronics that only produce 1w of charging current for the batterys, and on the other hand have a 5w panel and electronics and get 4.5w of charging current....HUH, so what the diff??

FACT, as soon as you rise the current comming from a panel, the voltage drops, if you lower the current voltage rises....don't worry about understanding that bit yet....

long story short, its all about the electronics after the panel, not the power the panel is rated at. As with out a Max Power Point Tracker, you have little hope of getting full power from your panels, as, when you hook up a battery for charging , the voltage is dragged down to battery voltage...HUH?? if you had a 20v panel putting out 500mA, hook up a 5v battery, and you get from the panel 5v @ 500mA, you basicly lose the voltage from the panels you got over 5v...yes this system works, as thats how its done on your roof, 20v of panels, but lots of them, dragged down to charge a 12v battery via PWM...or 40v panel to 24v battery or what ever...thats how its done... good if you have lots of room...

we can't do that for our trips as we have little room, so we need to maximize the power from each panel, thus use a MPPT for an increase of 30% in power per given footprint...MPPT works by fiding that sweet spot in the power triangle, for MAX input power at ALL light conditions. Only one store bought portable solar charger has MPPTing built into it that I know of.

And this is why for most solar chargers, panel power does NOT = Input charging power, and rated power on the device is rated at the ONE peak power point, the best one...as the unit does not track peak power, there one and only peak is when its full sun, at the purfect angle, this is why, rated outputs on consumer solar chargers are misleading, and have given solar chargers a bad name.....hope this helps....Kerry